package binary_tree.LeetCode;

import java.util.LinkedList;
import java.util.Queue;

public class Num958 {
    public boolean isCompleteTree(TreeNode root) {
  if(root==null){
      return true;
  }
        Queue<TreeNode> queue=new LinkedList<>();
        queue.offer(root);
        boolean isSecond=false;
        while(!queue.isEmpty()) {
          TreeNode cur=queue.poll();
            if (!isSecond) {
                if (cur.left != null && cur.right != null) {
                    queue.offer(cur.left);
                    queue.offer(cur.right);
                }
               else if (cur.left == null && cur.right != null) {
                    return false;
                }
               else if (cur.left != null) {
                    queue.offer(cur.left);
                    isSecond=true;
                }else{
                    isSecond=true;
                }
            }else{
                if(cur.left!=null||cur.right!=null){
                    return false;
                }
            }
        }
        return true;
    }
}
